SIOUX CITY -- It's been nearly 20 years since the threat of Missouri River flooding has caused serious concern in the Sioux City metro area, but there's reason to worry now.

With heavy rains over the past month up the river in Montana, North Dakota and western South Dakota -- totals that surpassed the rainfall expected for the entire year -- the U.S. Army Corps of Engineers is attempting to manage the river to reduce flooding risk.

Corps Brigadier Gen. John McMahon issued a statement Thursday warning that releases from the Missouri River's six dammed reservoirs will hit historic levels and that significant flooding is possible for hundreds of miles from Sioux City to the river's confluence with the Mississippi River west of St. Louis. On the Nebraska side of the river, Scenic Park Campground in South Sioux City had flooding Wednesday, and campers moved out of the lowest-lying area of the park.

Several Dakota County, Neb., law enforcement and fire departments met Thursday afternoon to discuss a response plan for rising river waters. Dakota County Civil Defense Director Pat Foust said he was not recommending evacuation for residents of low-lying areas near the Missouri just yet.

"We are in a preparedness stage. The people who live along the river probably have a history with the river, and they know whether or not they need to be taking action today," Foust said. "They know that much better than we do because they live there and they watch that river year in and year out."

"What our concerns are is to make sure that if it does get worse, that we are ready to protect the public, ready to protect public infrastructure and that we are not standing there knee-deep in water, saying, 'Well, do you suppose we shoulda talked about this?' That would not be good," Foust said.

Just up the river in South Dakota, officials with the Dakota Dunes Community Improvement District were busy preparing sandbags and trying to determine just how far the river will rise, given the large releases announced by the corps, and what impact that could have on the approximately 2,500 people who live in the community. Community Manager Jeff Dooley said officials are waiting to see an updated flooding forecast the corps is expected to make next week.

"Until we have that information, we're just preparing sandbags and getting pumps lined up," he said.

Dunes resident Becki Knepper said although residents of the Meadows, the area where she lives, aren't as worried as they would be if they lived closer to the river, they hope the corps doesn't release too much water.

"I think we're probably thinking that surely they'll hold back some of the water so that it doesn't get any fuller," she said.

The corps' McMahon warned that any flooded areas could be inundated for months. Flood stage at Sioux City is 30 feet -- a mere 3.5 feet above Thursday's level.

"People along the river are encouraged to make evacuation plans to protect their possessions and property," McMahon said.

Flows from five of the six dams will reach a record 110,000 cubic feet per second, well in excess of the previous high point of 70,000 CFS in 1997. McMahon said that action is being taken to prevent the dam spillways from being overtopped, which would make flooding even worse. Those releases will begin Saturday and reach peak level by late June or early July.

If heavy storms continue -- on Wednesday, Sioux City received a record for May 25 of nearly 3 inches of rain -- the corps will take additional steps, McMahon said. A later than normal mountain snowpack melt is an added complication.

South Dakota Gov. Dennis Daugaard on Thursday warned of imminent flooding in the capital city of Pierre. Later in the day he declared a 15-mile slow-driving, no-wake zone for the Missouri River from the confluence of the Big Sioux River at mile marker 734, then upstream to the Rosenbaum boat landing at mile marker 749.

Iowa Department of Natural Resources River Programs Outreach Coordinator Todd Robertson is warning recreational users of Iowa rivers to be aware of higher levels and faster flows. In Northwest Iowa, the Big Sioux River is the primary waterway of concern.

"The Big Sioux is flowing at a nasty 10,000 CFS, which is high and fast. Paddling on the Big Sioux is not recommended," Robertson said.

Bill Klohs of Le Mars, Iowa, check out his boat Thursday at Mlr Tym Marina along the Missouri River in Sioux City and said the water is the highest he's seen it since 1993. He's been boating on the Missouri since 1977.

"This is a big concern to us, having it so high," added his wife, Connie Klohs.

The Klohs plan to boat on the Missouri all three days of the Memorial Day weekend, the kickoff to summer activities. After scoping out the river, they determined it would still make for enjoyable boating.

"There is some debris floating, more than usual. That is what you have to watch out for," Bill Klohs said.